ON THE STRENGTH OF DUCTILE PARTICLE-REINFORCED BRITTLE-MATRIX COMPOSITES

This study examines theoretically the strength characteristics of ductile particle reinforced brittle materials in which the strength enhancement is derived from the crack bridging process. The crack bridging is characterized by rectilinear and linear softening bridging laws that relate the crack surface traction to the crack opening displacement. The composite strength is expressed in terms of two non-dimensional parameters that combine the effects of the flaw size, elastic modulus, matrix toughness, and the bridging-law parameters. It is shown that such composites can be substantially more flaw tolerant than the monolithic matrices owing to a narrowing of the strength distribution. The role of interface debond length is also examined. It is shown that there exists optimal debond lengths of which the composite strength is maximized. In contrast, the steady state toughness increases monotonically with debond length. The implications of these results on the design of composite microstructures are briefly described.